Sportsjacket !? What sport do you intend participating in?.
Now if you were to wear a Regimental blazer, then it's all buttons buttoned and Regimental tie, (Decorum will allow a carafe if your on a tiger hunt),maybe naked with a red sock over your knob may make the impression your looking for ?
But if you what to look like some twat from Miami mice well thatâ€™s better than the 45 year old Bart Simpson look, 'Cos the righteous truth is, there ain't nothing worse than some fool lying on some Third World beach wearing spandex, psychedelic trousers.

I'm heading to do a couple high-profile presentations. I'm not a dapper dandy dude. Help

I say just the top one until you sit down, thenm undo that one also. , but if this is all you have to worry about, either your gonna knock their socks off, or you need to go back and see if you put enough effort into your presentation. Either way, good luck!